The Stovebolt Site Forums The Shop Area Engine Shop Glass Bowl Fuel Filter

Hello All,

I just replaced my fuel pump and fuel filter in the glass bowl located near my carburetors.

The truck runs great!

I am noticing that soon after turning off the engine, the fuel in the glass bowl slowly starts emptying. Air bubbles are present and fuel level slowly drops. See attached picture.

I don't see any fuel leaks from any of the metal lines. I have a hard line from the fuel pump to this fuel filter, and I have hard lines from the fuel filter to all 3 carbs. This was all there originally.

Before I changed the fuel pump and fuel filter, I never saw the fuel level drop in the glass bowl.

Is it normal to have the fuel level drop?

If not, how do you suggest I debug this situation?

Also, the original fuel filter looked different. It seemed to be more like a brown hard ceramic material. It just popped out when I pulled on it. The new filter seemed to go in okay, but nothing seems to be holding it in place. I thought it would just fall into the glass bowl. However it never did fall into the glass bowl and things seem to be running great. Am I missing something here?

Thank you all for your help!

I believe there's supposed to be a small spring at the bottom of the glass reservoir that holds the filter against the top housing. At least that's the way the ones I used 50-something years ago worked. The "air" you're seeing after shut down is probably vaporized fuel created by the under hood temperature. As soon as the fuel pump kicks in, the pressure and the gas flow through the filter prevents the evaporation from happening while the engine is running.
Jerry

Gig,

I just checked a couple filters i have on the shelf. If yours is an AC filter/housing, they don't seem to use the spring that Jerry mentions. The filter is a press-in fit, from what I can tell.

On the other hand, if it's a Durex-Moraine filter/housing (which was what was commonly installed as an option in the early '50's) or an old Carter aftermarket filter, then it should have a cone-shaped spring between the bowl and filter just as Jerry says. See the image of the old brochure, attached. You can see the spring in the Durex filter illustration.

Since it happens "soon" after turning off the engine, the fuel in the glass bowl slowly starts emptying, I would suspect a leaky check valve inside of the fuel pump, maybe some dirt there.

Thank you DrDoug and 52Carl!

I do have an AC filter. So no spring! It is staying in place... so I think we are good to go!

I did put in a brand new fuel pump... So you might be right... maybe there is a problem with my check valve. Do I need to dismantle the new fuel pump and look for dirt? Or is there an easy way to clean it out? Thanks again!

If the engine runs OK, just ignore it. Some people lie awake at night wondering why the kitchen sink faucet isn't dripping.
Jerry

I would be patient, I bet after some run hours on the new fuel set-up that it will straighten itself out, if not then do as Jerry said.

Is it possible that fuel is being sucked back into the engine mixing with the oil ???


Fuel pump rebuilder

http://www.classicpreservation.com/fuelpumpkits.html


George
'54 3600

Would bet Jerry is correct about the vaporized fuel.

Fuel expansion/leak

The fuel filter acts as an "expansion tank" to relieve some of the pressure. Fuel is forced by the fuel valve in the carburetor.

Jon.

I may be facing the problem. The filter housing, glass and top, is original GM. The top of the filter has a metal flange that the filter is attached to. If I put the gasket on, then the filter, the filter drops to the bottom of the glass. I put the filter on,then the gasket, and the i.d. of the gasket holds the filter in place. Have no idea of that is correct. BTW, I purchased a brand new fuel pump for the car. Installed it and it didn’t pump a drop of gas. Reinstalled the 62 year old pump and it works. The old story about junk parts from other places.
Side bar: purchased a new light switch. Removed shaft from old one and installed in new one to bench test before installation. Now the new one will not release the shaft. More junk parts?

Very interesting read Jon, makes total sense. The OP looks like he has twice the possibility of the problem because of dual carbs.
I have the same setup but single carb, ie hard lines and fittings with the filter bowl without the problem, only difference is I refuse to run the 10% Alky fuel--there lies the problem possibly.
With that said, junk new parts from foreign places is very valid in my opinion too, especially those aftermarket bulb sockets, that dont want to fit into the guage clusters without a prayer.

Well what if the water main broke and floods the back 40 and drowns all of the livestock? Hmmm? (I am channeling my wife here.)

I'm with you on your brief suggestion. No sense breaking what ain't fixed yet. Or something like that...